Propellant powder



UNITED STATES PATENT OFFICE PROPELLANT POWDER Richard G. Woodbridge, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application October 8, 1936, Serial No. 104,667

2 Claims. (Cl. 52-13) My invention relates to an improved propel- The following composition is illustrative of one lant powder of the double-base type, that is, embodiment of the type of double-base powder containing both nitroglycerine and nitrocellulose, grains which I have found satisfactory for suband to a process for making the same. eq n u f ce re m by my ss:

5. Progressive burning nitrocellulose powders of Part 5 the surface treated type and possessing entirely satisfactory ballistic stability during storage have of 12'90 to nitrogen" been known for many years. These powders are made by surface treating powder grains with gfigzi gz gggg g kkygg5 gi 0 various moderating agents, preferably those ZGLn" 10 which when liquid are solvents for the nitro- The nitrocellulose will preferably be a blend of cellulose or a portion of the same. Various dethe type soluble in ether-alcohol with the type grees of improvement in ballistics are obtainable, ns ub ether-alcohol. the mixture a n a depending on the ballistic qualities of the powder nitrogen content in the neighborhood of 12.90 to 7:, grams t t th unt nd ature of the 13.25%, but not limited to such. The amount of 15 moderating agent and the process used for treatnitroglycerine may be varied. ment The nitrocellulose blend is dehydrated in a Surface treated double-base powders have Dre s y the Conventional method u n ethyl heretofore been unsatisfactory because of their alcohol, the excess of alcohol being removed by lack of ballistic stability. This has been attribpressure. The dehydrated nitrocellulose is bro- 2O uted to the probability that the moderating agent ken up and placed in the mixing machine, toapplied to the surfaces of the powder grains congether with the finely pulverized potassium sultinues to diffuse thruout the grains during storphate, if the latter is used. The nitroglycerine, age. This results in objectionable if not also plus stabilizer, is dissolved in acetone and graduhazardous change in the ballistic properties of ally added to the nitrocellulose. The ingredients the powder and ammunition containing the same. are mixed for one to wo hour r until a satis- Brunswig, in his book, Das Rauchlose Pulver, factory colloid of uniform compositionisobtained. page 101, indicates that the surface treatment of The colloid is then formed into blocks which are powder grains is limited to powder grains having pressed through dies into strings with or withlarge surface area, and principally to rifle powout central perforations or into ribbons which 30 ders, the object being to modify the burning speed are cut up into grains by means of a powder on the outer surface and adjacent layers without cutting machine. It will be understood that the affecting the interior. He further states that powder grains referred to subsequently are cylinwith nitrocellulose powder the effect is caused drical grains with central perforation, although 5 by supplemental treatment of the surface, while the process described is applicable to grains of with nitroglycerine powders the same method of other form. The powder grains are dried for treatment cannot be applied and other methods several days by means of warm air at a temmust be used. These other methods discussed perature of about 55 C. until the volatile solby Brunswig do not involve surface treatment of vents, acetone and alcohol, are substantially double-base powder grains. removed. 0

The principal object of my invention is an im- The base gra n Powder, e as desc bed in proved progressive burning double-base powder the foregoing, may then be surface treated with possessing a high order of ballistic as well as diethyldiphenylurea in the following illustrative chemical stability. Other objects will appear as manner: the description proceeds. 100 parts by weight of the powder grains are 45 In accordance with my invention the presence placed in a revolving drum together in the double-base powder of any ingredient such with preferably from about two to six parts by as Vaseline or starch which might tend to retard weight of diethyldiphenylurea, although these the impregnation of the powder grains by the proportions may be varied within the scope of moderating agent and by the process which I use my invention. The powder is then wet and par- 50 is preferably avoided. Where I find it necessary tially covered with water. Steam is admitted to to obtain fiashless results, I prefer to incorporate the mixture through an opening in the drum and in the powder a small amount of potassium sulthe water and powder maintained at a temperaphate in accordance with my U. S. Patent ture of about to C. for one-half hour 5 1,838,345. during which time the drum and contents are 55 other liquid. Instead of a revolving drum, there may be used any suitable container provided with means of agitation. The ratio of water to powder used will depend to some extent on the apparatus used for surface treating the powder grains. The coated and partially impregnated powder grains are then removed from the drum and subjected to a further impregnation treatment in hot water, preferably at a temperature of about 65 to 75 C., but not limited to such, for about 24 to 72 hours depending on the web thickness of the powder grains in order to cause further impregnating of the nitroglycerinenitrocellulose colloid by the diethyldiphenylurea.

After the impregnating treatment has been finished, the powder is dried and glazed. The

. improvement in ballistics which is obtained is very substantial and permanent as will be illustrated by the following ballistic results on two powders of the double-base type, one surface treated according to my invention using diethyldiphenylurea as the moderating agent, and the other powder surface treated with dlethylphthalate.

Additional tests have confirmed the above results, thus proving that the double-base powder surface moderated in the manner described with diethyldiphenylurea is ballistically stable while powder surface moderated with diethylphthalate was ballistically unstable.

My invention is particularly applicable to powder grains intended for use in military rifles and machine guns because it is for this purpose that previous attempts to make progressive burning double base powders of satisfactory ballistic stability have been unsuccessful. It is also to be understood that my process is applicable in general for the preparation of double base powders of the impregnated type for use in all kinds of small arms such as revolvers, pistols, shotguns and rifles.

While I prefer to use diethyldiphenylurea as the surface moderatingagent, it should be understood that the composition of my double-base powder grains and the process which I use for surface treating the same may tend to facilitate the successful use of other moderating agents having similar properties and performing a like function in a similar manner.

As many apparent and widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that I do not limit myself to the foregoing examples or descriptions except as indicated in the following patent claims.

I claim:

1. A double-base powder grain having its surface impregnated with diethyldiphenylurea and capable of maintaining its ballistic stability when stored at a temperature of 55 C. for approximately one month.

2. A double-base powder grain having its surface treated with diethyldiphenylurea in the presence of water at a temperature of 60 to 75' C., and capable of maintaining its ballistic stability when stored at a temperature of 55 C. for approximately one month.

RICHARD G. WOODBRJDGE. 

